This invention relates to a tensioning device for use in connection with a curtain having an endless, elastic traverse which is adjustable in both directions by a rotational drive means.
One of the problems in curtain systems having an endless elastic traverse is that the traverse experiences elastic linear expansion as a result of strain. The additional elongation of the traverse can produce a braking or blocking of the traverse.
Various tensioning devices are known for use with strip curtains and/or conventional curtains which attempt to solve this expansion problem. These tensioning devices also can be used for curtain systems with large and heavy traverses.
Swiss Pat. No. 420,520 discloses a tensioning means wherein drawing of the traverse is accomplished through a connecting link, which is attached between the ends of the traverse and which is coupled to a pull cord or the like. Cord stretchers are also known which hold the traverse under tension to compensate for stretching of the traverse. Moreover, tensioning devices are known which use adjustable drive pulleys and/or deflection pulleys.
However, these prior art devices are not able to compensate for large linear expansions of the traverse, which must then from time to time be stretched back or replaced. Also, these prior art devices have the disadvantage that the tension provided is often too great for the system.